Exam 3 Britton Renal Physiology I Flashcards
(104 cards)
1
Q
Functions of the kidney
What is excreted?
A
- Metabolic waste products
- Chemicals and other bioactive substances
2
Q
Functions of the kidney
What is regulated?
A
- H2O and electrolyte balance
- Acid-base balance
- Arterial blood pressure
- Red blood cell production (erythropoietin)
- Vitamin D production
3
Q
____ is the functional unit of the kidney
A
Nephron
4
Q
Each kidney contains ____ nephrons
A
~ 1 million
5
Q
The kidneys are well ____. Compared to other organs, blood flow is ____
A
Vascularized; high
6
Q
Kidneys receive ____ % of the cardiac output at rest
A
25% (5 L/min, 1.25 RBF L/min or 180 L/day)
7
Q
____ is necessary to expose the blood to filtration
A
High blood flow
8
Q
Blood enters each kidney via a ____. Then branches into ____, ____, ____
A
Renal artery; interlobar arteries, arcuate arteries, interlobular arteries
9
Q
How many capillary networks does the nephron have?
A
2
10
Q
What are the capillary networks of the nephron?
A
- Glomerular capillaries
- Peritubular capillaries (vasa recta)
11
Q
Which arterioles deliver blood to the glomerular capillaries?
A
Afferent arterioles (1st set of arterioles)
12
Q
Which arterioles deliver blood to the peritubular capillaries?
A
Efferent arterioles
13
Q
____ are the resistance vessels. The greatest drop in pressure occurs where?
A
Arterioles; Afferent and efferent arterioles
14
Q
What is renal blood flow determined by?
A
Renal artery blood pressure and resistance in arterioles
15
Q
Blood arrives at the kidneys via the ____ artery at ____
A
Renal artery; MAP (100 mmHg)
16
Q
True or false: pressure in the glomerular capillary is low
A
False - it is high and constant, which is needed for filtration
17
Q
Across different sections of renal blood vessels, pressure drops off in _____
A
Peritubular capillaries
18
Q
What are the steps of urine formation?
A
- Filtration
- Reabsorption
- Secretion
- Excretion
19
Q
During ____, plasma is filtered from the blood
A
Filtration
20
Q
What happens during reabsorption?
A
Water and solutes are reabsorbed from the glomerular filtrate into the peritubular capillaries
21
Q
What happens during secretion?
A
Metabolic waste and other substances are secreted from peritubular capillary blood into the nephron tubular fluid
22
Q
During ____, the remainder of fluid is excreted as urine
A
Excretion
23
Q
During the formation of urine, ____ L of filtrate per day yet only ____ L urine is produced
A
180; 1.5
24
Q
____% of substances are reabsorbed and returned to circulation. What would happen if reabsorption did not occur?
A
> 99%; Most of the constituents of ECF would be rapidly lost in the urine
25
The proximal tubule is a key site for ____
Reabsorption (some filtrate substances are also reabsorbed in distal segments of the nephron)
26
What does urinary excretion of a substance depend on?
Its filtration, reabsorption, and secretion
27
What is the equation for amount of solute excreted?
Amount filtered - amount reabsorbed + amount secreted = Amount of solute excreted
28
____ is the first step in the formation of urine
Glomerular filtration
29
Where does filtration occur?
Renal corpuscle
30
What does the renal corpuscle consist of?
- Glomerular capillaries
- Bowman's capsule
31
During glomerular filtration, what is filtered?
Low molecular weight substances that are freely dissolved in plasma
32
List examples of substances that are filtered during glomerular filtration
- Glucose
- Electrolytes (ions)
- Amino acids
- Peptides
- Waste products (creatinine, urea)
- H2O
- Drugs
33
What is NOT filtered during glomerular filtration?
- Cells (RBC, WBC, platelets)
- Proteins
- Lipoproteins
34
During glomerular filtration, ____ selects what molecules are filtered from the blood
The specialized structure of the glomerular filtration membrane
35
What is a filter?
A sieve that excludes solutes and proteins by electrical charge and size
36
What are the components of the glomerular filtration barrier?
- Glomerular capillary endothelial cells
- Glomerular basement membrane
- Filtration slit diaphragm
37
Describe the structure and function of glomerular capillary endothelial cells
- Flattened and highly fenestrated, resembling a sieve
- Allow ultrafiltration of the blood
37
____ carries a net negative charge that repels proteins. Why does this happen?
Glomerular basement membrane; Proteins also carry a negative charge
38
The filtration slit diaphragm contains specialized epithelial cells called:
Podocytes
39
Podocytes project "tentacle-like" foot processes that ensheath the ____
Glomerular capillaries
40
Podocyte foot processes ____, leaving ____ between them. The slits are bridged by a ____ that prevents proteins and large molecules from entering the ____
Inter-digitate; narrow slits; filtration slit diaphragm; Bowman space
41
Glomerular filtration depends on the balance of ____ that act across the glomerular filtration barrier
Starling forces
42
What are the 4 Starling forces present during glomerular filtration?
- 2 hydrostatic pressures (1 in capillary blood Pgc, 1 in interstitial fluid Pbs)
- 2 osmotic/colloid pressures (1 in capillary blood Tgc, 1 in interstitial fluid Tbs)
43
____ is the sum of the hydrostatic and osmotic pressures that drive fluid out of the blood capillary to form the glomerular filtrate
Net filtration pressure
44
In the glomerulus, Starling forces always favor ____
Filtration (always a positive number)
45
What is the formula for net filtration pressure?
(Pgc + Tbs) - (Pbs + Tgc)
Forces favoring filtration - opposing filtration
46
What is Kf?
Glomerular ultrafiltration coefficient
47
What is the formula for Kf?
Surface area x capillary wall condictivity/integrity
48
Vasoconstriction of the afferent arteriole - how is GFR likely to change?
- Hydrostatic pressure in glomerular capillaries (Pgc) will fall
- GFR will decrease
49
Vasoconstriction of the efferent arteriole - how is GFR likely to change?
- Pgc will increase
- GFR will increase
50
A kidney stone obstructs the ureter - how is GFR likely to change?
- Hydrostatic pressure in Bowman's capsule (Pbs) will increase
- GFR will decrease
51
A decrease in plasma protein concentration due to protein malnutrition - how is GFR likely to change?
- Colloid pressure in the glomerular capillaries will fall
- GFR will increase
52
In the glomerulus, Starling forces always favor ____
Filtration
53
In peritubular capillaries, Starling forces favor ____
Reabsorption
54
What is the formula for blood flow?
Q = delta pressure/resistance
55
Pressure is provided by ____. Resistance is provided mainly by ____
Systemic blood pressure (MAP); arterioles
56
Kidneys have an ____ mechanism to maintain constant renal blood flow despite variations in blood pressure
Autoregulation
57
In response to MAP variations in the range of ____ mmHg, autoregulation prevents changes to ___ and thus ____
80-180 mmHg; RBF; GFR
58
RBF is maintained by altering what?
The resistance of afferent and/or efferent arterioles
59
True or false: afferent and efferent arteriole resistance cannot be altered independently from each other
False - they can
60
Autoregulation is mediated by what 2 mechanisms?
- Myogenic response
- Tubulo-glomerular feedback
61
The myogenic response is also known as:
the Bayliss effect
62
What is the myogenic response?
- Constriction or dilation of afferent/efferent arterioles
- Intrinsic mechanism independent of neural mechanisms
63
The myogenic response involves ___ control of arteriole resistance by ____
Local; Local vasoactive substances
Local control is exerted through the direct action of local metabolites on arteriolar resistance
64
Vasoactive substances have the effect of _______ arterioles, thus increasing or decreasing ___ respectively through this vascular effect
Constricting or dilating; MAP
65
Overall, the ____ of the arterioles stabilizes RBF and thus GFR
Myogenic response
66
The tubulo-glomerular feedback is mediated by _____
Juxtaglomerular apparatus (JGA)
67
What does the juxtaglomerular apparatus consist of?
- Afferent and efferent arterioles
- Macula densa cells
- Distal tubule
- Mesangial cells
68
In tubulo-glomerular feedback, juxtaglomerular cells function as ____
Intra-renal baroreceptors
69
In tubulo-glomerular feedback, juxtaglomerular cells produce ___ which leads to the production of ____
Renin; ANG II (a potent vasoconstrictor)
70
In tubulo-glomerular feedback, what do macula densa cells monitor?
- The flow rate of filtrate through the DCT
- NaCl composition of filtrate
71
In response to changes detected in the filtrate, macula densa cells release ____ which control arteriole resistance in a paracrine mechanism. Macula densa cells can also stimulate JG cells to release ____
ATP and adenosine; renin
72
What are some properties of inulin?
- Freely filtered
- Not reabsorbed or secreted
73
What substance is used to measure GFR?
Inulin
74
What is PAH?
Para-aminohippurate
75
What are some properties of PAH?
- Freely filtered
- Not reabsorbed
- Fully secreted
76
What substance is used to measure effective renal plasma flow?
PAH
77
____ is the amount of plasma that is completely cleared of any given substance per unit time
Renal clearance
78
Know the renal clearance equation
Review equations
79
Glomerular filtration rate is a measure of:
How well your kidneys filter blood
80
____ is the volume of filtrate formed by both kidneys per minute
GFR
81
Inulin is a substance that is freely filtered at the ____ but is neither ___ or ____ along the remainder of the tubule. ____% of inulin that filters into the tubule is excreted
Glomerulus; reabsorbed or secreted; 100%
82
____ is used to estimate GFR
Creatinine
83
What is creatinine?
A metabolic breakdown product of skeletal muscle creatine
84
Creatinine is ____ and not ___, but it is ____, causing what?
Freely filtered; Reabsorbed; Secreted; 10-20% overestimate of GFR
85
True or false: Serum creatinine may be measured to monitor kidney function
True
86
What is the normal GFR for males?
125 mL/min
87
What is the normal GFR for females?
105 mL/min
88
GFR declines with:
- Age
- Chronic kidney disease
89
GFR <15 mL/min indicates:
Kidney failure
90
In a clearance ratio, the clearance of any substance can be compared with the clearance of ____
Inulin
91
Clearance ratio = 1.0 when:
X equals the clearance of inulin
92
Clearance ratio > 1.0 when:
Substance x is filtered and secreted
93
Clearance ratio < 1.0 when:
- X is not filtered
- X is filtered and subsequently reabsorbed
94
Renal plasma flow (RPF) is measured from the clearance of ____
PAH
95
What is the value of effective RPF?
~ 600 mL/min
96
10% of the PAH that passes through the kidney escapes ____
Secretion
97
PAH clearance underestimates RPF by ____
10%
98
Know the formula for renal blood flow
RPF/1-hematocrit
99
Formula for filtration fraction
GFR/RPF
100
____ is the fraction of the RPF that is filtered across the glomerular capillaries
Filtration fraction
101
Normal filtration fraction value
16-20%
102
What is filtered load?
Amount of a substance filtered across the glomerular filtration membrane per unit time
103
What is excretion rate?
Amount of a substance excreted in the urine per unit time
